What good is a toy that will wind down? What if you could put a heart in one? A real heart. One that beat and beat and didn't stop. What couldn't you do if you could make a toy like that? From the moment Mathias becomes the owner of a mysterious piece of paper, he is in terrible danger. Entangled in devious plots and pursued by the sinister Doctor Leiter and his devilish toys, Mathias finds himself on a quest to uncover a deadly secret.